Suicide and Self-Harm Among Immigrant Youth to Ontario, Canada From Muslim Majority Countries: A Population-Based Study

OBJECTIVE

To examine the association between Muslim religious affiliation and suicide and self-harm presentations among first- and second-generation immigrant youth.

METHODS

We performed a population-based cohort study involving individuals aged 12 to 24 years, living in Ontario, who immigrated to Canada between 1 January 2003 and 31 May 2017 (first generation) and those born to immigrant mothers (second generation). Health administrative and demographic data were used to analyze suicide and self-harm presentations. Sex-stratified logistic regression models generated odds ratios (OR) for suicide and negative binomial regression models generated rate ratios (aRR) for self-harm presentations, adjusting for refugee status and time since migration.

RESULTS

Of 1,070,248 immigrant youth (50.1% female), there were 129,919 (23.8%) females and 129,446 (24.2%) males from Muslim-majority countries. Males from Muslim-majority countries had lower suicide rates (3.8/100,000 person years [PY]) compared to males from Muslim-minority countries (5.9/100,000 PY) (OR: 0.62, 95% CI, 0.42-0.92). Rates of suicide between female Muslim-majority and Muslim-minority groups were not different (Muslim-majority 1.8/100,000 PY; Muslim-minority 2.2/100,000 PY) (OR: 0.82, 95% CI, 0.46-1.47). Males from Muslim-majority countries had lower rates of self-harm presentations than males from Muslim-minority (<10%) countries (Muslim majority: 12.2/10,000 PY, Muslim-minority: 14.1/10,000 PY) (aRR: 0.82, 95% CI, 0.75, 0.90). Among female immigrants, rates of self-harm presentations were not different among Muslim-majority (30.1/10,000 PY) compared to Muslim-minority (<10%) (32.9/10,000 PY) (aRR: 0.93, 95% CI, 0.87-1.00) countries. For females, older age at immigration conferred a lower risk of self-harm presentations.

CONCLUSION

Being a male from a Muslim-majority country may confer protection from suicide and self-harm presentations but the same was not observed for females. Approaches to understanding the observed sex-based differences are warranted.

Depression versus dementia: is this construct still relevant?

Cognitive impairment has long been identified as a component of late-life depression (LLD), and depressive symptoms are common in neurodegeneration. Depression may confer a greater risk of cognitive decline in a cognitively intact population and further cognitive decline in a mild cognitive impairment population compared with those without depression. Exploration of the link between cognitive impairment in LLD and the depressive features of neurodegeneration is an essential part of a diagnostic algorithm. In this review, we will discuss these links; we will address depressive symptoms as a risk factor for dementia and as a prodrome to dementia. We will review clinical subtypes and imaging markers as predictors of development of dementia in depressed patients and explore vascular etiologies. We will also explore LLD and dementia as a spectrum, rather than mutually exclusive diagnostic entities.

The impact of hot melt extrusion and spray drying on mechanical properties and tableting indices of materials used in pharmaceutical development

The impact of melt extrusion (HME) and spray drying (SD) on mechanical properties of hypromellose acetate succinate (HPMCAS), copovidone, and their formulated blends was studied and compared with that of reference excipients. Tensile strength (TS), compression pressure (CP), elastic modulus (E), and dynamic hardness (Hd ) were determined along with Hiestand indices using compacts prepared at a solid fraction of ∼0.85. HPMCAS and copovidone exhibited lower Hd , lower CP, and lower E than the reference excipients and moderate TS. HPMCAS was found to be highly brittle based on brittle fracture index values. The CP was 24% and 61% higher for HPMCAS after SD and HME, respectively, than for unprocessed material along with a higher Hd . Furthermore, the TS of HPMCAS and copovidone decreased upon HME. Upon blending melt-extruded HPMCAS with plastic materials such as microcrystalline cellulose, the TS increased. These results suggest that SD and HME could impact reworkability by reducing deformation of materials and in case of HME, likely by increasing density due to heating and shear stress in a screw extruder. A somewhat similar effect was observed for the dynamic binding index (BId ) of the excipients and formulated blends. Such data can be used to quantitate the impact of processing on mechanical properties of materials during tablet formulation development.

A neurohistochemical blueprint for pain-induced loss of appetite

A common complaint among pain patients is that they lose their appetite. These accounts are anecdotal, however, and the neural mechanism underlying pain-induced loss of appetite remains unknown. In this study, we documented the occurrence of appetite loss in patients under migraine attack and investigated the neuronal substrate of pain-induced anorexia in our animal model of intracranial pain. We found that loss of appetite during the migraine attack in humans coincided strongly with the onset and duration of the head pain in 32/39 cases, and that brief noxious stimulation of the dura in conscious rats produced a transient suppression of food intake. Mapping of neuronal activation in the rat showed that noxious dural stimulation induced a 3- to 4-fold increase in the number of Fos-positive neurons in medullary dorsal horn areas that process nociceptive signals (laminae I, V) and in parabrachial and hypothalamic neurons positioned to suppress feeding behavior. In the parabrachial area, activated neurons were localized in the superior-lateral subnucleus, and 40% of them expressed the mRNA encoding the anorectic neuropeptide cholecystokinin. In the hypothalamus, activated Fos-positive neurons were found in the dorsomedial area of the ventromedial nucleus, and 76% of them expressed the mRNA for cholecystokinin type-B receptor. Based on these findings, we suggest that at least one of several groups of hypothalamic neurons that normally inhibit appetite in response to metabolic cues is positioned to mediate the suppression of food intake by pain signals.

Peripheral and central sensitization during migraine

Current theories propose that the pain of migraine is caused by chemical activation of meningeal perivascular fibers. In an animal model of migraine, we have recently shown that chemical activation of meningeal primary afferent nociceptors that innervate the dura could lead to the following: a) peripheral sensitization of these nociceptors to intracranial mechanical stimulation; b) central sensitization of second-order trigeminovascular neurons that receive convergent input from the dura and skin to extracranial mechanical and thermal stimulation; and c) facilitated cardiovascular pressor responses that are usually indicative of pain. These findings provide the first set of evidence for the induction of peripheral and central sensitization along trigeminovascular pain pathways by visceral input from the intracranial dura. We propose that the throbbing pain of migraine is mediated mainly through peripheral and to a lesser extent through central sensitization, and that the development of scalp tenderness is mediated mainly through central sensitization.

Trigeminohypothalamic and reticulohypothalamic tract neurons in the upper cervical spinal cord and caudal medulla of the rat

Sensory information that arises in orofacial organs facilitates exploratory, ingestive, and defensive behaviors that are essential to overall fitness and survival. Because the hypothalamus plays an important role in the execution of these behaviors, sensory signals conveyed by the trigeminal nerve must be available to this brain structure. Recent anatomical studies have shown that a large number of neurons in the upper cervical spinal cord and caudal medulla project directly to the hypothalamus. The goal of the present study was to identify the types of information that these neurons carry to the hypothalamus and to map the route of their ascending axonal projections. Single-unit recording and antidromic microstimulation techniques were used to identify 81 hypothalamic-projecting neurons in the caudal medulla and upper cervical (C(1)) spinal cord that exhibited trigeminal receptive fields. Of the 72 neurons whose locations were identified, 54 were in laminae I-V of the dorsal horn at the level of C(1) (n = 22) or nucleus caudalis (Vc, n = 32) and were considered trigeminohypothalamic tract (THT) neurons because these regions are within the main projection territory of trigeminal primary afferent fibers. The remaining 18 neurons were in the adjacent lateral reticular formation (LRF) and were considered reticulohypothalamic tract (RHT) neurons. The receptive fields of THT neurons were restricted to the innervation territory of the trigeminal nerve and included the tongue and lips, cornea, intracranial dura, and vibrissae. Based on their responses to mechanical stimulation of cutaneous or intraoral receptive fields, the majority of THT neurons were classified as nociceptive (38% high-threshold, HT, 42% wide-dynamic-range, WDR), but in comparison to the spinohypothalamic tract (SHT), a relatively high percentage of low-threshold (LT) neurons were also found (20%). Responses to thermal stimuli were found more commonly in WDR than in HT neurons: 75% of HT and 93% of WDR neurons responded to heat, while 16% of HT and 54% of WDR neurons responded to cold. These neurons responded primarily to noxious intensities of thermal stimulation. In contrast, all LT neurons responded to innocuous and noxious intensities of both heat and cold stimuli, a phenomenon that has not been described for other populations of mechanoreceptive LT neurons at spinal or trigeminal levels. In contrast to THT neurons, RHT neurons exhibited large and complex receptive fields, which extended over both orofacial ("trigeminal") and extracephalic ("non-trigeminal") skin areas. Their responses to stimulation of trigeminal receptive fields were greater than their responses to stimulation of non-trigeminal receptive fields, and their responses to innocuous stimuli were induced only when applied to trigeminal receptive fields. As described for SHT axons, the axons of THT and RHT neurons ascended through the contralateral brain stem to the supraoptic decussation (SOD) in the lateral hypothalamus; 57% of them then crossed the midline to reach the ipsilateral hypothalamus. Collateral projections were found in the superior colliculus, substantia nigra, red nucleus, anterior pretectal nucleus, and in the lateral, perifornical, dorsomedial, suprachiasmatic, and supraoptic hypothalamic nuclei. Additional projections (which have not been described previously for SHT neurons) were found rostral to the hypothalamus in the caudate-putamen, globus pallidus, and substantia innominata. The findings that nonnociceptive signals reach the hypothalamus primarily through the direct THT route, whereas nociceptive signals reach the hypothalamus through both the direct THT and the indirect RHT routes suggest that highly prioritized painful signals are transferred in parallel channels to ensure that this critical information reaches the hypothalamus, a brain area that regulates homeostasis and other humoral responses required for the survival of the organism.

Cardiovascular and neuronal responses to head stimulation reflect central sensitization and cutaneous allodynia in a rat model of migraine

Reduction of the threshold of cardiovascular and neuronal responses to facial and intracranial stimulation reflects central sensitization and cutaneous allodynia in a rat model of migraine. Current theories propose that migraine pain is caused by chemical activation of meningeal perivascular fibers. We previously found that chemical irritation of the dura causes trigeminovascular fibers innervating the dura and central trigeminal neurons receiving convergent input from the dura and skin to respond to low-intensity mechanical and thermal stimuli that previously induced minimal or no responses. One conclusion of these studies was that when low- and high-intensity stimuli induce responses of similar magnitude in nociceptive neurons, low-intensity stimuli must be as painful as the high-intensity stimuli. The present study investigates in anesthetized rats the significance of the changes in the responses of central trigeminal neurons (i.e., in nucleus caudalis) by correlating them with the occurrence and type of the simultaneously recorded cardiovascular responses. Before chemical stimulation of the dura, simultaneous increases in neuronal firing rates and blood pressure were induced by dural indentation with forces >/= 2.35 g and by noxious cutaneous stimuli such as pinching the skin and warming > 46 degrees C. After chemical stimulation, similar neuronal responses and blood pressure increases were evoked by much smaller forces for dural indentation and by innocuous cutaneous stimuli such as brushing the skin and warming it to >/= 43 degrees C. The onsets of neuronal responses preceded the onsets of depressor responses by 1.7 s and pressor responses by 4.0 s. The duration of neuronal responses was 15 s, whereas the duration of depressor responses was shorter (5.8 s) and pressor responses longer (22.7 s) than the neuronal responses. We conclude that the facilitated cardiovascular and central trigeminal neuronal responses to innocuous stimulation of the skin indicate that when dural stimulation induces central sensitization, innocuous stimuli are as nociceptive as noxious stimuli had been before dural stimulation and that a similar process might occur during the development of cutaneous allodynia during migraine.

Cells of origin of the trigeminohypothalamic tract in the rat

Recent studies have demonstrated that a large number of spinal cord neurons convey somatosensory and visceral nociceptive information directly from cervical, lumbar, and sacral spinal cord segments to the hypothalamus. Because sensory information from head and orofacial structures is processed by all subnuclei of the trigeminal brainstem nuclear complex (TBNC) we hypothesized that all of them contain neurons that project directly to the hypothalamus. In the present study, we used the retrograde tracer Fluoro-Gold to examine this hypothesis. Fluoro-Gold injections that filled most of the hypothalamus on one side labeled approximately 1,000 neurons (best case = 1,048, mean = 718 +/- 240) bilaterally (70% contralateral) within all trigeminal subnuclei and C1-2. Of these neurons, 86% were distributed caudal to the obex (22% in C2, 22% in C1, 23% in subnucleus caudalis, and 18% in the transition zone between subnuclei caudalis and interpolaris), and 14% rostral to the obex (6% in subnucleus interpolaris, 4% in subnucleus oralis, and 4% in subnucleus principalis). Caudal to the obex, most labeled neurons were found in laminae I-II and V and the paratrigeminal nucleus, and fewer neurons in laminae III-IV and X. The distribution of retrogradely labeled neurons in TBNC gray matter areas that receive monosynaptic input from trigeminal primary afferent fibers innervating extracranial orofacial structures (such as the cornea, nose, tongue, teeth, lips, vibrissae, and skin) and intracranial structures (such as the meninges and cerebral blood vessels) suggests that sensory and nociceptive information originating in these tissues could be transferred to the hypothalamus directly by this pathway.

Chemical stimulation of the intracranial dura induces enhanced responses to facial stimulation in brain stem trigeminal neurons

Chemical activation and sensitization of trigeminal primary afferent neurons innervating the intracranial meninges have been postulated as possible causes of certain headaches. This sensitization, however, cannot explain the extracranial hypersensitivity that often accompanies headache. The goal of this study was to test the hypothesis that chemical activation and sensitization of meningeal sensory neurons can lead to activation and sensitization of central trigeminal neurons that receive convergent input from the dura and skin. This hypothesis was investigated by recording changes in the responsiveness of 23 [16 wide-dynamic range (WDR), 5 high threshold (HT), and 2 low threshold (LT)] dura-sensitive neurons in nucleus caudalis to mechanical stimulation of their dural receptive fields and to mechanical and thermal stimulation of their cutaneous receptive fields after local application of inflammatory mediators or acidic agents to the dura. Responses to brief chemical stimulation were recorded in 70% of the neurons; most were short, lasting the duration of the stimulus only. Twenty minutes after chemical stimulation of the dura, the following changes occurred: 1) 95% of the neurons showed significant increases in sensitivity to mechanical indentation of the dura: their thresholds to dural indentation changed from 1.57 to 0.49 g (means, P < 0.0001), and the response magnitude to identical stimuli increased by two- to fourfold; 2) 80% of the neurons showed significant increases in cutaneous mechanosensitivity: their responses to brush and pressure increased 2.5- (P < 0.05) and 1. 6-fold (P < 0.05), respectively; 3) 75% of the neurons showed a significant increase in cutaneous thermosensitivity: their thresholds to slow heating of the skin changed from 43.7 +/- 0.7 to 40.3 +/- 0.7 degrees C (P < 0.005) and to slow cooling from 23.7 +/- 3.3 to 29.2 +/- 1.8 degrees C (P < 0.05); 4) dural receptive fields expanded within 30 min and cutaneous receptive fields within 2-4 h; and 5) ongoing activity developed in WDR and HT but not in LT neurons. Application of lidocaine to the dura abolished the response to dural stimulation but had minimal effect on the increased responses to cutaneous stimulation (suggesting involvement of a central mechanism in maintaining the sensitized state). Antidromic activation (current of <30 muA) of dura-sensitive neurons revealed projections to the hypothalamus, thalamus, and midbrain. These findings suggest that chemical activation and sensitization of dura-sensitive peripheral nociceptors could lead to enhanced responses in central neurons and that this central sensitization therefore could result in extracranial tenderness (mechanical and thermal allodynia) in the absence of extracranial pathology. The projection targets of these neurons suggest a possible role in mediating the autonomic, endocrine, and affective symptoms that accompany headaches.

Antihistamines in the treatment of asthma

Antihistamines were investigated for use in asthma shortly after discovery over fifty years ago. Earlier compounds proved ineffective because of side effects: this class of drugs was not thought useful for asthma, and were actually considered contraindicated. More recent drugs have greater potency, fewer side-effects, and no evidence of adverse effects in asthma. There are some studies showing second generation antihistamines, especially cetirizine, improve certain parameters of asthma.

Evaluation of selenium exposure in copper refinery workers

Concentrations of selenium in plasma and urine and activity of glutathione peroxidase in erythrocytes were determined in workers exposed to selenium and in a control group. Plasma selenium concentrations were significantly lower in exposed workers compared to the controls. Erythrocyte glutathione peroxidase activity in selenium workers was significantly higher than in the control subjects. Urine selenium concentrations were not statistically different between the two groups. There was a significant positive correlation between plasma selenium concentrations and urine selenium concentrations in workers exposed to selenium. A weak significant positive correlation was found between plasma selenium concentrations and erythrocyte glutathione peroxidase activity in exposed workers. Our results suggest that the lower plasma selenium concentrations in selenium workers may be attributed to an increase of urinary selenium excretion.

Dorsal horn projection targets of ON and OFF cells in the rostral ventromedial medulla

1. The rostral ventromedial medulla (RVM) participates in the modulation of nociceptive transmission by spinal cord neurons. Previous anatomic studies have demonstrated that RVM neurons project to laminae I, II, and V of the dorsal horn; laminae VII and VIII of the intermediate and ventral horns; the intermediolateral column; and lamina X. The RVM contains at least three physiologically defined classes of neurons, two of which, the ON and the OFF cells, have been implicated in nociceptive modulation. Because these cells classes are intermingled in the RVM, it has not been possible to determine the spinal laminar projection targets of ON and OFF cells by anatomic methods. Therefore in the current study we employed antidromic microstimulation methods to determine the laminar projections of two of the three classes of RVM neurons, the ON and the OFF cells. 2. In lightly anesthetized (with methohexital sodium) rats, single-unit extracellular recordings were made from 48 RVM neurons that were physiologically characterized as ON (30) or OFF (18) cells. The recording locations of 45 of these neurons were recovered. Thirty-seven were found in the nucleus raphe magnus and eight were located near its dorsal and lateral borders. 3. Thirty-two physiologically identified RVM neurons (18 ON and 14 OFF cells) were antidromically activated from the cervical spinal cord using a monopolar stimulating electrode. The stimulating electrode was moved systematically in the white matter until antidromic activation could be produced with currents of < or = 20 microA (6.1 +/- 0.7 microA, mean +/- SE). The points from which minimum currents were required to antidromically activate the neurons were located mainly in the ipsilateral dorsolateral funiculus (DLF) (27 of 32). In a few cases, lowest antidromic threshold currents were found near the border between the DLF and ventrolateral funiculus (VLF) or, rarely, in the VLF itself. In these cases, the cell recordings were found to be near the dorsal boundary of the RVM. 4. While one electrode was used to stimulate the parent axon in the lateral funiculus, a second was used to explore the gray matter for the presence of collateral branches. The identification of a branch was initially determined by an increase in antidromic latency. At the same rostrocaudal plane of the spinal cord, stimulation of the DLF induced an antidromic spike that invaded the neuron earlier than the antidromic spike elicited by stimulation in the gray matter. Collateral branches were confirmed by establishing that the location of the minimum threshold point for antidromic activation of the neurons from the second electrode was in the gray matter, that the minimum current required to antidromically activate the neuron from that point was too low to activate the parent axon in the DLF, and that a collision occurred between the spikes induced by the two stimulating electrodes. 5. In 17 cases, physiologically identified RVM neurons (10 ON and 7 OFF cells) were antidromically activated from the gray matter of the cervical spinal cord using a current of 8.4 +/- 2.1 (SE) microA. Minimum threshold points for antidromic activation were found in laminae I-II (3 ON and 4 OFF cells), lamina V (5 ON and 6 OFF cells), and regions ventral to the lateral reticulated area (3 ON and 2 OFF cells) of the gray matter. As indicated by these numbers, some neurons were antidromically activated from more than one gray matter region. In general, all OFF cells and 9 of 10 ON cells were antidromically activated from low threshold points in either laminae I-II or lamina V. 6. In six cases, neurons were activated from separate points located in two or three different laminae of the gray matter. Three OFF cells were activated from laminae I-II and V, one OFF cell and one ON cell were activated from lamina V and from more ventral points, and one ON cell was activated from laminae I-II and from points ventral to lamina V.

Reduction and elimination of encephalitis in an experimental glioma therapy model with attenuated herpes simplex mutants that retain susceptibility to acyclovir

Malignant gliomas are the most common malignant brain tumors and are almost universally fatal. A genetically engineered herpes simplex virus-1 mutant with decreased neurovirulence, dlsptk, has been shown to kill human glioma cells in culture and in animal models. However, intracranial inoculation of dlsptk is limited by fatal encephalitis at higher doses. Therefore, additional engineered and recombinant herpes simplex mutants with demonstrated reduced neurovirulence (AraAr9, AraAr13, RE6, R3616) were examined as antiglioma agents. One long-term human glioma cell line and two early-passage human gliomas in culture were destroyed by all four viruses tested. In a subcutaneous glioma model, AraAr13, RE6, and R3616 retained substantial antineoplastic effects in nude mice when compared with controls (one-sided Wilcoxon rank test, P < 0.05 for one or more doses each). When tested in a nude mouse intracranial glioma model, both RE6 and R3616 significantly prolonged average survival without producing premature encephalitic deaths at two doses (log-rank statistic, P < 0.007). Histopathological studies of the brains of surviving animals revealed minimal focal encephalitis in two of three RE6-treated animals and no evidence of encephalitis in either one of three RE6-treated or in three of three R3616-treated animals. No evidence of residual tumor was seen in four of the six surviving animals. Additionally, both RE6 and R3616 were found to be susceptible to the common antiherpetic agent acyclovir, adding to their safety as potential antiglioma agents. Recombinant and engineered viruses that minimize host toxicity and maximize tumoricidal activity merit further study as antineoplastic agents.

Inhibition of angiogenesis and growth of human nerve-sheath tumors by AGM-1470

The effectiveness of AGM-1470, a potent, fungal-derived inhibitor of angiogenesis, in suppressing the neovascularization and growth of human Schwann cell tumors was tested in six schwannomas, seven neurofibromas, and one neurofibrosarcoma. Tumor fragments from surgical specimens were implanted into the subrenal capsule of 348 nude mice (nu/nu). Seven days after implantation, the tumors were measured and vascularity was graded. The animals were then randomly assigned to one of two groups, to receive either saline (control group) or systemic AGM-1470 treatment. After 2 to 6 weeks of treatment, tumor size and degree of vascularity were recorded. In the six different schwannomas implanted into 138 mice, the average vascular grade in the control group after 2 weeks of treatment increased from 2.2 to 3.2 (+1.0), while in the AGM-1470-treated group it decreased from 2.2 to 1.7 (-0.5) (p < 0.01). In the seven different neurofibromas implanted into 158 mice, the change in the average vascular grade in control and AGM-1470-treated animals was +0.5 and -1.0, respectively (p < 0.01). In the one neurofibrosarcoma implanted into 52 mice, the change in average vascular grade in each group during the 6-week treatment period was +1.9 and -1.0, respectively (p < 0.01). Neurofibrosarcoma growth after 6 weeks of AGM-1470 treatment was only 8.5% of the growth found in the control animals (p < 0.01). This study determined that AGM-1470 is effective in inhibiting angiogenesis and the growth of human nerve-sheath tumors.

Expanded spectrum of viral therapy in the treatment of nervous system tumors

Despite aggressive therapy, many nervous system neoplasms, including malignant gliomas, medulloblastomas, malignant meningiomas, and neurofibrosarcomas, maintain high mortality rates. The authors recently utilized a thymidine kinase-negative herpes simplex-1 mutant virus, dlsptk, with reduced neurovirulence, for the effective treatment of malignant human gliomas in cell culture and in nude mouse in vivo models. The range of human nervous system tumors that might be responsive to viral therapy is now expanded. Three medulloblastoma, four malignant or atypical meningioma, and five neurofibrosarcoma cell lines or early-passage tumors were treated with the dlsptk virus in cell culture. A cell death rate of at least 99% was evident in every tumor tested for at least one multiplicity of infection within 14 days after treatment. Control tumor cell cultures remained viable. To test dlsptk therapy in vivo, the authors treated human medulloblastoma subcutaneous xenografts with two doses of dlsptk. Mean growth ratios were significantly inhibited in the treated group when compared to control tumors, and there was a significant number of tumor regressions in the treated animals. Similar results were seen with human malignant meningioma xenografts in a subrenal capsule study. These results encourage the further investigation of viral therapy in the treatment of a broad spectrum of nervous system tumors refractory to conventional treatment methods.

Selective killing of glioma cells in culture and in vivo by retrovirus transfer of the herpes simplex virus thymidine kinase gene

The thymidine kinase gene (tk) of herpes simplex type 1 virus (HSV-1) was inserted into a retroviral vector under the transcriptional control of the enhancer-promoter element of the Moloney murine leukemia virus long terminal repeat. Replication-defective viral particles were obtained by transfection of vector DNA into the packaging cell line psi2 and were used to infect C6 rat glioma-derived cell lines in culture. The sensitivity of these cells to the toxic effects of the nucleoside analog ganciclovir was found to be significantly increased by transfer of the HSV-1 tk gene. The difference in sensitivity between infected and uninfected cells defined ganciclovir concentrations that could be used to selectively kill essentially all infected cells while sparing uninfected ones. C6 glioma cells introduced subcutaneously into nude mice were highly tumorigenic. Growth of tumors produced from C6-derived cells bearing the HSV-1 tk gene, but not parental C6 cells, could be inhibited by intraperitoneal administration of ganciclovir. This work demonstrates the effectiveness of the thymidine kinase expressed by the HSV-1 ks gene in sensitizing brain tumor cells to the toxic effects of nucleoside analogs. Retrovirus vectors should thus prove useful in the selective delivery of this killer gene to dividing tumor cells in the nervous system, where most endogenous cells are not dividing.

Experimental therapy of human glioma by means of a genetically engineered virus mutant

Malignant gliomas are the most common malignant brain tumors and are almost always fatal. A thymidine kinase-negative mutant of herpes simplex virus-1 (dlsptk) that is attenuated for neurovirulence was tested as a possible treatment for gliomas. In cell culture, dlsptk killed two long-term human glioma lines and three short-term human glioma cell populations. In nude mice with implanted subcutaneous and subrenal U87 human gliomas, intraneoplastic inoculation of dlsptk caused growth inhibition. In nude mice with intracranial U87 gliomas, intraneoplastic inoculation of dlsptk prolonged survival. Genetically engineered viruses such as dlsptk merit further evaluation as novel antineoplastic agents.

Gene delivery to glioma cells in rat brain by grafting of a retrovirus packaging cell line

Retrovirus vectors only integrate into the genome of dividing cells and can thus be used to selectively infect tumor cells in the adult rat brain. Gene delivery was assessed by using the retrovirus BAG vector, which bears the Escherichia coli lacZ gene under the MoMLV LTR promoter-enhancer element, and by histochemical staining for bacterial beta-galactosidase activity. Direct injection of this vector (90-900 cfu) into the adult rat brain, with or without prior inoculation of C6 glioma cells (2 x 10(5) cells) resulted in labeling of only a few cells as assessed 1 week later. When the psi 2-BAG packaging line was grafted into the brain, labeled psi 2-BAG cells could be found after 1 day, but not after 5 days, following grafting, suggesting that the grafted cells had been rejected and that no endogenous cells had integrated released vector, or that expression of lacZ had been turned off. In contrast, when the psi 2-BAG packaging line was grafted into a brain region, which had been inoculated previously with rat C6 glioma cells (2 x 10(5) cells), beta-galactosidase labeling of these tumor cells, identified by immunocytochemistry for glial fibrillary acidic protein and S100, could be demonstrated 10 days later. Thus, grafting of retrovirus packaging lines into adult brain provides a mean to infect tumor cells in situ. The grafted packaging cells may continue to release retrovirus particles for an extended period, thus infecting more cells at the stage of division appropriate for viral integration, as compared to inoculation of the virus alone. Grafting of retrovirus packaging cell lines could be used to selectively deliver "killer" or "suppressor" genes to tumor cells in the brain to curtail their growth.

Development of a chemotherapeutic model for microfilaricidal drugs to Dirofilaria immitis

Microfilariae obtained from in vitro culture of adult Dirofilaria immitis were inoculated into naive dogs and used to test the in vivo efficacy of the antimicrofilarial drug Dizan. Injection of 33 million microfilariae into a 3-month-old male beagle pup over a 5-day period resulted in a microfilaremia that peaked at 863 microfilariae per ml on day 30. Treatment with Dizan resulted in a rapid clearance of microfilariae from the peripheral circulation. Four additional male beagle pups that were each given a total of 31 million microfilariae over 100 days maintained an average of 25 microfilariae per ml for 2 months. Microfilaremias were monitored by ELISA, a modified Knott's method and selected blood chemistry tests. It was shown that after residing in the peripheral circulation the microfilariae were able to develop into infective larvae in mosquitoes; therefore, the system may be a reasonable model of the natural microfilaremic state.